1. Field of the Invention
The invention relates to a method for the determination of an analyte in a liquid sample, especially a body liquid sample, as well as to an analytical apparatus and a computer program product.
2. Description of Related Art
As a supplement or an alternative, the determination of an analyte in the liquid sample can also comprise, in addition to the basic detection of the analyte itself, the measuring of analyte-specific properties in the liquid sample. Here, the liquid sample to be examined is customarily applied on a test system or test element with several analyte detection zones that are also designated as measuring- or examination areas. For example, the applied liquid sample moves here along a straight line on which the several measuring areas or detection zones are arranged. Analyte-specific catch structures are arranged in the measuring areas that can have a circular, rectangular or linear form, so that a part of the analyte from the liquid sample is bound in the measuring areas.
The analyte or analytes is/are customarily labeled directly or via antibodies and as a result are prepared for a subsequent optical evaluation of the test system. A preparation of the test system or test element can optionally comprise the cleaning or washing with a puffer solution, diluting solution or a wash solution. Finally, the test system, that is, for example, a dry chemical test element, can then be evaluated by optical sampling in order in particular to determine the occurrence of one or more certain analytes in the measuring areas.
In the optical sampling, which is also designated as optical scanning, measuring light beams produced in the scanned examination areas are detected with a detector apparatus after leaving the examination areas. The measuring light beams can be produced by radiating test light beams produced for their part by a suitable monochromatic or polychromatic light source onto the measuring areas charged with optically active substances to be measured. In the measuring areas the light of the test light beams then interacts with the optically active substances so that a corresponding change of the optical properties of the test light beams results that then leave the measuring area as measured light beams. During the radiating in of test light the absorption, the transmission, the reflection or also the fluorescence can be examined as optical properties of the measuring light beams. Furthermore, measuring light beams can be based on a luminescence of the optically active substances in the measuring areas.
During the optical sampling of the test element/test system, for example, the test element and the detector apparatus which detects the measuring light beams or the test element and the light source can be shifted relative to one another in order to optically analyze measuring area after measuring area in this manner.
The measuring areas are optically examined with the aid of optical measuring methods such as absorption, fluorescence, transmission or reflection in order to analyze the binding of the analytes in a particular zone. Here the so-called test light beams are put on the measuring area that then interact in the measuring area with optical labels that bind to the analyte-specific catch structures, as a result of which the measuring light beams are produced, that are detected with the aid of an optical detector apparatus. For example, a photodiode or a photodiode arrangement can serve as such optical detector apparatuses. The signals measured for the measuring light beams are used in order to determine, for example, a concentration or other properties of the analyte in the liquid sample.
The detected measuring light beams are customarily dependent on the binding efficiency with which a complex of the analyte flowing past the measuring area or the detection zone binds there to the catch structures. The binding efficiency is for its part generally dependent on different properties such as the type of the substrate (membrane) used for the measuring area, the individual liquid sample, the analyte-specific catch structures or the temperature. The binding efficiency is therefore very different for different measuring- or analytical situations. This means that a variation of the binding efficiency usually directly affects the result of analysis.